1. Field of the Invention
The invention relates to a construction for indicating the remaining amount of sheets contained in a sheet containing portion provided in an image forming apparatus.
2. Description of the Related Art
In an image forming apparatus of an electrophotographic printing type or an electrostatic recording type such as a conventional copying machine, a laser beam printer (LBP) or a facsimile apparatus, provision is made of a sheet feeding apparatus for feeding sheets stacked in a sheet containing portion to an image forming portion.
As such a sheet feeding apparatus, there is known one provided with a feed roller which is sheet feeding means for feeding out sheets from a sheet feeding cassette which is a sheet containing portion, and a sheet separating member urged against the surface of the feed roller to prevent the double feeding of sheets to be fed.
Now, when for example, images are to be formed on a great deal of sheets at a time, if the remaining amount of sheets contained in a sheet feeding cassette is unknown, there is liable to occur an inconvenient state such as the state that the timing for supplying sheets cannot be known and the work is interrupted in the course of the job.
So, in order to prevent the occurrence of such an inconvenience, there is an apparatus in which for example, a sensor as remaining amount detecting means is disposed in a sheet feeding cassette, and the remaining amount of sheets is adapted to be indicated on the control panel of the image forming apparatus based on information from this sensor. However, in a case where as described above, the remaining amount of sheets is detected by the use of a sensor, the construction of remaining amount detecting means becomes complicated and this leads to an increased cost and therefore, there has been required a sheet remaining amount indicating mechanism of a simple construction.
So, as disclosed in Japanese Patent Application Laid-open No. H04-243742, there is an apparatus which is pivotally provided in a sheet feeding cassette and in which a pointer is mounted on a sheet stacking plate on which sheets are stacked and an indication scale for indicating the remaining amount of sheets is provided on the main body of the sheet feeding cassette. Design is made such that the pointer moves based on the movement of the sheet stacking plate, and the remaining amount of sheets is indicated by the position of the pointer relative to the indication scale (see, for example, Japanese Utility Model Application Laid-open No. S61-49746 and Japanese Patent Application Laid-open No. H04-243742). A user can see the sheet feeding cassette from the outside thereof to confirm the remaining amount of sheets in the sheet feeding cassette, and suitably effect the supplementation or the like of sheets.
Now, in a sheet feeding apparatus and an image forming apparatus, there is a case where if the sheet stacking plate is lifted, the leading edge of the uppermost one of the sheets stacked thereon remains nipped in the nip portion between separating means such as a separating pad or a separating roller and a feed roller. In such case, there is the problem that if the apparatus is left in that state for a long time, a fold will occur to the leading edge of the sheet to cause a faulty image or the jam of the sheet.
So, there has been proposed a construction in which when the feeding of sheets is completed, the sheet stacking plate is lowered and the stacked sheets and the feed roller are separated from each other.
However, in a case where as described above, the sheet stacking plate is lowered, a remaining amount indicating pointer mounted on the sheet stacking plate also moves. Accordingly, there has been the problem that in the case of sheet remaining amount indicating means designed to indicate the remaining amount of sheets by the position of the pointer based on the movement of the sheet stacking plate, the remaining amount of sheets cannot be accurately indicated when the sheet feeding operation is not performed.